This invention relates to a disk recording and/or reproduction apparatus and method, and more particularly to a disk recording and/or reproduction apparatus and method by which the inclination between a head for recording or reproducing information onto or from a disk and the disk can always be adjusted to a correct condition.
FIG. 15 shows a construction of an exemplary one of related art reproduction apparatus for an optical disk. Referring to FIG. 15, an optical disk 1 is rotated at a predetermined speed by a spindle motor 2. An optical head 3 irradiates a laser beam upon the optical disk 1 and receives reflected light from the optical disk 1. A skew sensor 4 is fixed to a common base (not shown) with the optical head 3 and detects a relative inclination between the optical head 3 and the optical disk 1.
A PLL (phase locked loop) circuit 5 binary digitizes a RF signal reproduced from a signal recorded on the optical disk 1 and outputted from the optical head 3 to produce a binary RF signal and extracts clocks included in the RF signal to produce a synchronizing clock signal. A CLV circuit 6 receives the binary RF signal and the synchronizing clock signal outputted from the PLL circuit 5 and outputs an error signal in phase between them. A switch 8 is controlled by a control circuit 17 to select one of the output of the CLV circuit 6 and the output of an initial driving circuit 7 and outputs the selected output to the spindle motor 2.
The optical head 3 produces a focusing error signal in accordance with, for example, a principle of an astigmatism method and further produces a tracking error signal in accordance with, for example, a principle of a push-pull method. A focusing servo circuit 9 receives the focusing error signal outputted from the optical head 3 and drives a focusing coil 12 in response to the focusing error signal to perform focusing control of the optical head 3 in a direction perpendicular to (toward or away from) the optical disk 1. A tracking servo circuit 10 receives a tracking error signal outputted from the optical head 3 and drives a tracking coil 13 in response to the tracking error signal to perform tracking control of the optical head 3 in a direction perpendicular to the direction of a track of the optical disk 1.
The skew sensor 4 generates a skew error signal corresponding to the inclination between the optical head 3 and the optical disk 1 and outputs the skew error signal to a skew servo circuit 11. The skew servo circuit 11 drives a skew motor 14 in response to the skew error signal to adjust the relative inclination of the optical head 3 with respect to the optical disk 1.
A signal outputted from the tracking servo circuit 10 is supplied to a thread servo circuit 15. The thread servo circuit 15 drives a thread motor 16 in response to the signal to move the optical head 3 in a radial direction of the optical disk 1. The control circuit 17 controls the focusing servo circuit 9, the tracking servo circuit 10, the skew servo circuit 11 and the thread servo circuit 15 as well as the switch 8.
When the optical disk reproduction apparatus is produced, after a disk for adjustment (standard disk) is loaded in position as the optical disk 1 into the optical disk reproduction apparatus, the control circuit 17 controls the thread servo circuit 15 to drive the thread motor 16 to feed the optical head 3 to a predetermined reference position (for example, the position of an innermost circumferential track) of the optical disk 1 (disk for adjustment). Then, the control circuit 17 changes over the switch 8 to the initial driving circuit 7 side so that an initial driving signal outputted from the initial driving circuit 7 is supplied to the spindle motor 2 via the switch 8 to drive the spindle motor 2.
Further, the control circuit 17 controls the focusing servo circuit 9 and the tracking servo circuit 10 to drive the focusing coil 12 and the tracking coil 13 in response to the focusing error signal and the tracking error signal outputted from the optical head 3 to perform focusing servoing and tracking servoing, respectively.
The switch 8 is changed over to the CLV circuit 6 side after the spindle motor 2 is driven for a predetermined period of time. The PLL circuit 5 binary digitizes a RF (radio frequency) signal reproduced from a signal recorded on the optical disk 1 by and reproduced from the optical head 3 to produce a binary RF signal and produces a synchronizing clock signal from the RF signal, and supplies the two signals to the CLV (constant linear velocity) circuit 6. The CLV circuit 6 compares the binary RF signal and the synchronizing clock signal in phase with each other and supplies an error signal between them to the spindle motor 2 via the switch 8. Consequently, the spindle motor 2 rotates the optical disk 1 so that the linear velocity of it may be fixed.
In this condition, the RF signal outputted from the optical head 3 is measured by a measuring instrument (not shown), and the skew servo circuit 11 is controlled by the control circuit 17 so that the amplitude of the RF signal may be maximum. The skew servo circuit 11 controls the skew motor 14 in accordance with the control from the control circuit 17 to adjust the relative angle of the optical head 3 with respect to the optical disk 1. When an optimum adjustment angle is reached, the RF signal exhibits a maximum amplitude. When the RF signal of the maximum amplitude is obtained, the adjustment of the skew servo circuit 11 is ended, and the adjustment value is fixed. As a result, the skew servo circuit 11 thereafter supplies the fixed value to the skew motor 14.
When an ordinary optical disk is loaded in position into and reproduced by the optical disk reproduction apparatus, a skew error signal corresponding to the relative angle of the optical head 3 with respect to the optical disk 1 is outputted from the skew sensor 4. The skew servo circuit 11 compares the skew error signal with the value set upon adjustment and outputs the error signal. The skew motor 14 adjusts the relative angle of the optical head 3 with respect to the optical disk 1 in response to the error signal. Consequently, the optical head 3 is adjusted to an appropriate angle with respect to the optical disk 1.
In the related art apparatus described above, since the inclination of the optical head 3 is adjusted using a disk for adjustment upon shipment of the apparatus from a factory and the inclination is thereafter fixed, there is a subject to be solved that the optical head 3 cannot be adjusted to an appropriate angle in accordance with a dispersion of an individual optical disk.
Further, there is another subject to be solved that, when the inclination of the optical head 3 or the skew sensor 4 changes as a result of a variation with respect to time (aging), it becomes difficult to correctly reproduce data recorded on an optical disk. Particularly where the optical disk 1 is a disk on which information is recorded in a high density such as, for example, a digital video disk (DVD), a displacement of the optical head 3 from an appropriate angle has a significant influence on a result of reproduction.